In process automation technology, field devices are often applied which serve for registering and/or influencing properties of a process. Serving for registering are sensors, such as, for example, fill level measuring devices, flow measuring devices, pressure- and temperature measuring devices, pH-redox potential measuring devices, conductivity measuring devices, etc., which register fill level, flow, pressure, temperature, pH value, or conductivity. Serving for influencing a process are actuators, such as, for example, valves or pumps, via which can be changed the flow of a liquid in a pipeline section or the fill level in a container. In principle, all devices which are applied near to the process and deliver or work with process-relevant information are referred to as field devices. A large number of such field devices are produced and sold by the firm Endress+Hauser.
In modern industrial plants, field devices are, as a rule, connected via fieldbus systems (e.g. Profibus®, Foundation® Fieldbus, HART®, etc.) (level 1) with one or more controllers, such as, for example, a PLC (programmable logic controller), a linking device or a gateway. The controller can, in such case, execute a control application for the connected field devices. For this, measured values, for example, registered by individual field devices, are transmitted via the fieldbus system of level 1 to the controller, and the controller outputs control commands to field devices as a function of these measured values. Additionally, in modern industrial plants, one or more superordinated units, especially OPC client(s) (OPC: OLE for Process Control), which serve as a visualizing system, monitoring system, archiving system, etc., are frequently connected via a superordinated network system (level 2), such as, for example, an HSE network system (HSE: High Speed Ethernet), and a linking device or a gateway with the fieldbus system of level 1. Such a superordinated unit can, in such case, be embodied for example as a SCADA system (SCADA: Supervisory Control and Data Acquisition). The linking device or gateway can simultaneously also execute control applications with regard to field devices of the fieldbus system of level 1.
In modern field devices, as a rule, different properties of the field device itself, properties of a process in which the field device is applied, and/or properties of a communication connection of the field device are monitored. Corresponding parameters, via which information concerning these properties is given, are provided in the field devices. Such parameters are especially provided in a field device which is designed according to the Foundation® Fieldbus bus system. These parameters can, in principle, be utilized for diagnosis of the field device and its environment. In the following, these parameters, which are provided in a field device, and through which information concerning one or more of the above set forth properties are given, and which accordingly are usable for diagnostic purposes, are referred to as diagnostic parameters. A group of such diagnostic parameters is formed by diagnostic parameters, which deliver information relative to the communication connection of the field device. Another group of such diagnostic parameters is formed by device-related diagnostic parameters, which deliver information concerning properties of the field device itself and/or concerning properties of a process, in which the field device is applied.
Up to the present, there have only been limited options for reading and effectively utilizing these diagnostic parameters from a field device for a diagnosis. An opportunity exists to read such diagnostic parameters from the field device via an operating tool. A user, who reads the particular diagnostic parameters via the operating tool must then decide, based on the particular values of these diagnostic parameters, whether a critical state is present, and whether a reengineering or other measures are required. For such purpose, the user must, however, have available a relatively comprehensive technical knowledge.
Further, some diagnostic modules are in electrical current supply units for a fieldbus system, while other diagnostic modules are not in electrical circuit supply units, through which the signal transferred via the respective communication connections is metrologically registered and analyzed. In this way, information concerning properties of the communication connections of the participants connected to the fieldbus system is gained. If diagnostic parameters which deliver information concerning the communication connection of a field device are outside of an allowable region or some other criterion for an alarm or error report is given, an alarm or error report is output via the diagnostic module.
There are additionally provided, internally in field devices, limit values for the particular diagnostic parameters of the diagnostic modules. If such a limit value is exceeded, the field device and/or a controller in communication connection with the field device then outputs/output an alarm or error report. Depending on which type of diagnostic parameter whose limit value is exceeded is involved, in given cases, the status of the measured value, which is output by the relevant field device, is set to “bad”. This means that the measured value is not usable. A user is then, as a rule, given an alarm or error report via a superordinated unit connected to the network system of level 2, for example via a visualizing system and/or a SCADA system.
In situations, in which an alarm or error report is given to the user (for example, via a superordinated unit connected to the network system of level 2 and/or via the diagnostic module mentioned above), a continued operation the plant is in part possible. Especially in the case of certain diagnostic parameters, the exceeding of a limit value can be uncritical for the operation of the plant as a whole, and/or the exceeding of a limit value can be caused by aging phenomena of the respective field device, field device component or of the respective communication connection, wherein a further operation of the plant is nevertheless possible. In other cases, in turn, the exceeding of a limit value of a diagnostic parameter is critical in such a manner, that the operation of the plant must actually be stopped. An operator (a service technician), who monitors such a superordinated unit and/or a diagnostic module (for the communication connection) on-site, does not, as a rule, have available sufficient technical knowledge to judge correctly the particular relevance of the occuring alarm or error reports. Accordingly, in the case of the occurrence of an alarm or error report, an operator is often compelled to stop the operation of the plant, even when the displayed alarm or error report is, in the specific situation, uncritical for the operation of the plant. Such down times of the plant lead to increased costs for the plant operator.
In DE 2005 063 055 A1, a method is described, in the case of which, in a field device, the development in time of a quality parameter for the communication connection of this field device—especially of a stale count parameter of this field device—is registered and evaluated. As a function of this development, in given cases, a limit value for the quality parameter is adapted in the field device. For registering and evaluating the time development, and, in given cases, for adapting the limit value, an expert system implemented in the field device can be applied. Via the method described in the DE 10 2005 063 055 A1, a comprehensive use of the diagnostic parameter provided by a field device is not possible. Additionally, this method does not enable various diagnostic parameters of the relevant field device and, in given cases, also various field devices, to be placed in relationship to one another, and further diagnostic information to be obtained therefrom.
On the basis of these considerations, an object of the present invention is to utilize the diagnostic parameters provided in a field device effectively for diagnosis, and to provide a user with diagnostic information in such a manner, that plant down times which are not absolutely required are prevented.